The efficient capture and recording of a photonic scene, often changing dynamically in time, lies at the heart of nearly all modern observational sciences. And while each discipline utilizes specialized instrumentation, there are three fundamental building blocks that are common to all approaches: fore-optics (meant to focus and sometimes disperse light spectrally), detection devices (which capture light and convert it to an analog signal), and digitization electronics (providing the conversion of the analog measurement to digital bits).
A goal of such instrumentation may be to capture and record the energy and polarization of each incoming photon, the location of each photon in the focal plane, and the time of arrival at the focal plane. If indeed every measurable property of every photon is saved digitally, then the building up a complete “movie” of the recorded scene would require post process binning spatially, spectrally, and temporally. As a practical matter, however, such binning is usually accomplished by the instrumentation itself: detectors are exposed for a finite integration time to collect a sufficient number of photons to overcome background and instrumentation noise. The spectral energy distribution (i.e., intensity of a function of wavelength) of the incoming light may be discerned by introducing spectral elements, such as diffraction gratings, into the fore-optics, and recording intensity differences across the spectrum at different spatial location on the detectors. In low-light scenes or in rapidly changing scenes, there is a fundamental trade-off between efficiency of photon detection including the quantum efficiency of detectors, spectral resolution, spatial resolution, and temporal resolution.